Superconductor Science and Technology · 1994 · 157 citations · 60 references
EngineeringMaterials EngineeringMaterials ScienceCondensed Matter PhysicsSolid State PhysicsSolidificationDirectional SolidificationSolidification KineticsSolidification ProcessingSuperconducting MaterialsCuprate SuperconductorsDefect EngineeringDislocation DensityFlux PinningHigh-temperature Deformation MechanismsHigh-temperature SuperconductorsMagnetic PropertiesTexturing
Melt processing is the leading method for fabricating bulk YBa₂Cu₃Oₓ(123) because of its superior transport and magnetic properties, yet its growth rate is limited by Y‑diffusion‑controlled growth, the size and distribution of Y₂BaCuO₅ precipitates, and the requirement for slow cooling and growth to maintain a stable 123 planar front. The study aims to use seeded directional solidification to produce large, single‑domain YBa₂Cu₃Oₓ samples with a‑b planes aligned along the sample axis. The authors employ seeded directional solidification together with defect engineering—introducing twins, irradiation damage, second‑phase inclusions, and high‑temperature mechanical deformation—to enhance flux pinning and reduce Jc anisotropy. Flux‑pinning enhancement has progressed, with high‑temperature deformation increasing dislocation density, improving critical current density, and reducing its anisotropy.
Melt processing is the most prominent method utilized in the fabrication of bulk YBa2Cu3Ox(123) because of the superior transport and magnetic properties of this material. Due to the Y-diffusion-controlled growth mechanism of 123, the maximum allowable growth rate is sensitive to the size and distribution of the Y2BaCuO5 precipitates. In addition, a slow cooling rate and a slow growth rate have to be employed to maintain the stability of the 123 planar growth front. Among the many melt-texturing methods and modifications, seeded directional solidification has the potential to produce long single-domained samples of large cross-sectional area with the strongly superconducting a-b planes aligned along the sample axis. Steady progress has also been achieved in flux-pinning enhancement through defect engineering. This includes the introduction and modification of defects such as twins, irradiation damage and second-phase inclusions. In particular, high-temperature mechanical deformation has been shown to be effective in increasing the dislocation density and results in improved Jc as well as reduced Jc anisotropy.
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Flux pinning mechanisms in type II superconductors
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High critical currents in Y-Ba-Cu-O superconductors
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